Elastic thread



June 19, 1934. G. VAN VOORHIS ELASTIC THREAD Filed Nov. 15, 1933 ATTORNEY 'atented June 19, 1934 ELASTIC Q THREAD George S. Van Voorhis,

Northampton, Mass, as-

signor to United Elastic Corporation, Easthampton, Mass., a corporation of Massachusetts Application November 15, 1933, Serial N6. 698,143

19 Claims.

This invention relates to rubber thread.

It has been a common practice to weave or :nit fabrics in which rubber strands are included, :1 order to impart the desired degree of elasticity o the fabric. In some cases the rubber strands ire maintained separate from each other while [1 other instances, especially when greater.

;icity while avoiding the use of a single strand iaving a cross-sectional area approximately equal that of all the strands of the group. This con- ;truction is of advantage in the event that one itrand becomes broken for any reason. A common cause of such breakage is the knicking of me of the strands by the needle of a sewing machine. It is a characteristic of rubber thread shat when it is so knicked it will then break very easily. When a single strand is thus broken its ands separate and draw back into the goods due to the fact that the rubber is normally under considerable tension. If this strand is large, it produces a flaw in the goods that materially af- Eects its value as a salable article. On the other hand, if the rubber thread is composed of a plurality of strands, the breaking of one leaves the others undisturbed and therefore does not so seriously impair the goods, although such a product still would not pass a rigid inspection.

It is also a common practice to wind a cover of fibrous yarn or thread around one or more strands of rubber and to use this so-called "covered rubber thread instead of bare rubber thread in the manufacture of elastic fabrics. In other words, the rubber in a fabric may be either bare or covered, as desired, and the choice as to.which shall be used depends largely upon the character of the goods.

' In any of these goods in which bare rubber thread or covered rubber-thread or cord made up of two or more strands is used there is also a tendency for the strands to become misplaced. This action apparently is due at times to peculiar strains imposed on the strands during the manufacturing operations, more especially during the winding or covering step. In other cases it appears to be due to a difierence in tension on the individual strands. In fact, if a section of multiple core covered rubber thread is cut of! and the strands thereof are uncovered and measured, they will very frequently be found to be of different lengths. But whatever may be the cause, it is a common experience to find that the rubber strands in a group do not occupy a uniform relationship to each othenthroughout the goods but become displaced, one relatively to the other.

This occurs both in covered rubber and in bare rubber and it detracts from the desired smooth appearance of fabrics woven from such thread, tending to produce blisters or surface irregularities in the goods.

The present invention deals with the problems presented by these circumstances. It aims to improve rubber thread with -a. view to producing a more uniform product, preventing the relative shifting of the rubber strands in elastic fabrics and in covered rubber thread, and minimizing the flaws caused by broken strands.

The nature of theinvention will be readily understood from the following description when read in connection with the accompanying drawing, and the novel features will be particularly pointed out in the appended claims.

In the drawing,

Figure 1 is a perspective view of a short piece of covered rubber embodying this invention, the parts being shown on a large-scale;

Figs. 2 and 3 are sectional views through different parts of the covered rubber thread il 5- lustrated in Fig. I; I

Figs. 4 and 5 are views similar to Figs. 2-and 3, respectively, but illustrating another embodiment of the invention;

Figs. 6 and '7 are views similar to Figs. 2 and 3, respectively, but illustrating a further form which the invention may take;

Figs. 8 and 9 are views similar to Figs. 2 and 3, respectively, illustrating still another embodi-' ment of the invention;

Fig. 10 is a transverse, sectional view of a further modification; and

Figs. 11 and 12 are front and side views, partly in section, illustrating steps in the method of making the thread illustrated in Figs. 8 and 9.

The usual method of manufacturing rubber thread consists in slitting asheet or web of rubber to produce strands or threads substantially square in cross-sectional form. When two or more of these strands are brought together to make a core for a covered rubber thread, if their flat edges are abutted against each other and two of them are used, the resulting core is of rectangular form in cross-section, being approximately twice as wide as it is thick. Both threads n are under tension when the covering threads are wound around them, and there is always likely to be more or less twist in one or both strands. This fact, together with the fact that the faces of the threads are not in stable contact with each other is, I believe, responsible in a large measure for the tendency of the threads to become displaced, one relatively to the other, when they are included in a piece of goods. Such a tendency is even more pronounced when bare rubbers are used in groups in weaving a fabric.

I overcome the difliculties above described by bonding the strands directly to each other. For example, the thread illustrated in Figs. 1, 2 and 3 consists of two strands indicated, respectively, at 2 and 3, bonded together throughout their entire lengths. Such a thread may be used either bare or covered .in some suitable manner. As illustrated in Figs. 1 and 3, the rubber core has the usual wrappings 5 and 6 of yarn or thread wound around it. The bond or adhesion of the strands 2 and 3' to each other can be produced in different ways as, for example, by making the individual strands by the cutting or extrusion processes and subsequently uniting them. I prefer, however, to bond two sheets or webs of rubber directly together in face to face relationship, and thento cut or slit the composite sheet so formed to produce threads. A thread having substantially the form illustrated in Fig. 2 can be made conveniently in this manner, and because of the fact that the two strands are bonded directly to each other, any substantial slipping of one relatively to the other is prevented.

Whether the thread is made in this manner or by one of the other methods above described, it is desirable to make the individual strands of a rectangular form, or of some other shape which affords a broad surface contact between the strands. Such a cross-sectional form, even in the absence of a direct bond between the strands, would present a substantial advantage over the ordinary constructions, since the contact of the broad flat faces of the strands against each other throughout the length of the thread, in combination with the binding of these strands together by the wrapping yarns or threads 5 and 6, would I greatly increase the stability of the relationship between the strands, or, in other words, would tend to prevent the lateral displacement of one strand relatively to the other. And this feature is valuable in thread made according to the present invention, especially if the direct bond between the strands is made relatively weak because of the requirements of some individual use to be made of the thread.

In this connection itmay be pointed out that the rubber core for the thread shown in Fig. 1 has, when in its .free, untensioned and unrestrained condition, the cross-sectional form of a square, but is is divided into two strands, each of rectangular form. Thisis the most convenient form in which to manufacture a cut rubber thread. But when the threadsare made by the extrusion process the strands can be made in other cross-sectional shapes and can be brought together to produce a core having a cross-sectional form of a po ygon, circle, or other regular geometrical figure. It is desirable, however, that in any of these forms the width of each abutting face be greater than any cross-sectional dimension of either strand at right angles to said face..

Figs. 6 and 7 show a thread having a rubber core which, in its natural form, has the crossaddition, the fact that the sectional shape of a square but is divided along a diagonal into two strands the cross-sectional form of an isosceles triangle. When such a core is wound, as shown in Fig. 7, it has essentially the same form as that illustrated in Fig. 3. Figs. 8 and 9 show a core made up of two strands 9 and 10, each having a semicircular form, with their flat with each other.

While the bare thread shown in Figs. 2, 4 and 6 is of square form in cross-section when in its natural condition, such a thread is stretched or elongated very substantially during the wrapping or winding of the threads 'or yarns 5 and 6 around them, the degree of elongation varying with the requirements of a particular product, but in a typical case being in the neighborhood of 500%. Consequently, when the tensionon the rubber is released, it contracts longitudinally, expands laterally, stretching the covering, and assumes approximately a circular outline as illustrated in Figs. 3, 5 and 7. Such contraction is limited by adjacent'strands of wrapping thread abutting against each other.

When the thread is made by adhesively bonding two sheets or webs of rubber together and slitting or cutting them to form threads, the character of the union or bond so produced between the strands of an individual thread can be varied within very substantial limits. That is,

the two sheets of rubber can, for example, be

controlled and the identity of the individual sheets can be preserved to a greater or less degree as desired. It is preferable to use some talc between the sheets so that the sheets will not be united into a single integral homogeneous structure, the union, however, being such that the two strands of each thread cut from them will be definitely held in a fixed relationship to each other, but still being sufliciently independent so that the tear produced by knicking one thread with a needle will not travel through into the unknicked strand. If, therefore, one strand be- 7 and 8, each having faces in contact comes broken, the union of that strand to itscompanion strand may readily be made sufliciently strong to prevent the ends of the broken strand normally from separating greatly, but in any event the break in the latter strand will not' materially weaken the unbroken strand. This is an important advantage in either covered or uncovered rubber thread since it affords a control of the broken strand which has not been available heretofore, and makes a flaw in the goods caused by a broken strand much less conspicuous than otherwise would be the case. In two or more strands of a given core or rubber thread are directly bonded vtogether reduces the expense of handling the thread and preparing it for the market. It also results, when used as a core, in avoiding the difference in tension on the different strands of a core which has been partly responsible heretofore-for the'difliculties encountered in using covered rubber or gimp. In other words, the fact that the strands of the core are all united together, beginning with the time at which the thread is cut, avoids any differences in tension on individual strands, andit facilitates the maintenance of a more uniform tension on a multiplicity of such threads when used, for example, as warps in the manufacture of a woven fabric.

In this connection it may be pointed out that the wrapping of covered rubber thread sometimes is put on by braiding instead of winding. Either method may be used, as desired, for the purposes of this invention. It will also be understood that the number of strands used in a thread or in a core may be varied to suit the requirements of individual cases or the preferences of different manufacturers.

A further advantage of this product isthat the strands of a core or thread may be of different compositions. Sometimes this is desirable in order to produce unique color efiects, one strand being of a difierent shade from the other. A considerable variety in color combinations can be produced in this manner as, for example, in the arrangement illustrated in Figs. 4' and 5, where two strands 2' and 3' cut from a composite sheet made in the manner above described are united with two other strands 2" and 3" to form a bare thread or a core for a covered thread in which two, three or four colors may be used, as desired.

In some cases, also, one of the strands of a ply I thread embodying this invention may be utilized to limit the elongation of the latter. This may be done, for example, by making one of the strands of a different composition from the other, one being capable of greater elongation than the other. Such a thread is illustrated in Fig. 10, composed of two outside strands 13 bonded to the opposite sides of an intermediate strand 12. The latter may, for example, be made of some rubber compound which will have a relatively limited stretch, while the strands 13 are made of a much livelier composition or compound, thus giving to the composite thread the desired degree of elasticity while at the same time utilizing the much lower degree of stretch of the centralstrand 12 to limit the maximum elongation 0 which the entire thread is capable.

When the strands are made by the extrusion process, as above described in connection with Figs. 8 and 9, the strands for. an individual core or thread may be brought together as they issue from the apertures of the dies in which they are extruded, and thus be assembled and bonded together very conveniently. For example, an arrangement similar to that illustrated in Figs. 11 and l2 may be used in which .the two strands 9 and 10 are forced through the apertures of the extruding die 14 and 'are then brought together and fed between two driven rolls l5-15 having grooved peripheries. The fiat faces of the strands thus are brought together while the rubber is still in a very tacky or sticky condition and they can thus be bonded securely to each other. In order to prevent the bond so made from uniting the two strands into a single integral substantially homogeneous structure, a limited quantity of talc, or some other material capable of reducing the adhesion of the two strands to each other, may be blown or otherwise forced between the meeting surfaces of the strands. In Fig. 12 the tube 16 is shown arranged to direct a blast of powdered talc into the space between the two meeting surfaces of the strands. By properly controlling the quantity of talc so applied, the strength of the union or bond between the two strands may be varied substantially as desired.

While I have herein shown and described typiparallel strands of rubber bonded directly to each other and held by said bond in approximately a fixed relationship to each other.

2. A rubber thread comprising a plurality of parallel strands of rubber bonded directly to each other in a side by side relationship by a union ofiering considerable resistance to the separation of the strands but in which the strands are not integrally united.

3. A rubber thread comprising a plurality of parallel strands of rubber bonded directly to each other in a side by side relationship, one of said strands being of a different composition from another.

4. A rubber thread comprising a plurality of parallel strands of rubber bonded directly to each other in a side by side relationship, one or moreof said strands serving to limit the degree of stretch of another to a value below the maximum elongation of the latter.

5. A rubber thread comprising a plurality of parallel strands of rubber bonded directly to each other by a union which holds them in a predetermined relationship to each other substantially no throughout the length of the thread.

6. A rubber thread comprising a plurality of parallel strands of rubber bonded directly together by a union which holds them in a fixed longitudinal and lateral relationship to each other but does not integrally unite them.

7. A rubber thread comprising a plurality of parallel strands of rubber bonded directly together by a ,union which holds them in said parallel relationship but which prevents the breaking of one strand from materially weakening another to which it is so bonded.

8. A rubber thread comprising a plurality of parallel strands of rubber having their longitudinal surfaces abutting against each other and bonded directly .together in a stable and substantially non-slipping relationship throughout substantial proportions of their lengths.

9. A rubber thread comprising a plurality of parallel strands of rubber having their longitudinal surfaces abutting against each other and bonded directly together by a separable union which holds them normally in said parallel relationship and which offers substantial resistance to separation of the strands.

10. A rubber thread comprising a plurality of parallel strands of rubber bonded directly to-' gether by an adhesive union which holds them normally in a fixed relationship to each other substantially throughout the length of the thread, said union having less strength than the tensile strength of either strand.

11. A covered rubber thread comprising 9. pl rality of parallel strands of rubber having their longitudinal surfaces bearing against each other and bonded directly together in a stable and normally non-slipping relationship, and a wrapping of fibrous material closely encircling said strands. 12. A covered rubber thread comprising a plurality of parallel strands of rubber having their longitudinal surfaces bearing against each other and bonded directly together in broad surface contact with each other serving to prevent lateral slipping of one strand relatively to another, and a wrapping of fibrous material closely encircling said strands.

13. A covered rubber thread comprising a plurality of parallel strands of rubber having fiat longitudinal faces bearing against each other and bonded together to form a stranded core, the union between said faces serving to prevent lateral slipping of one strand relatively to another, and a wrapping of fibrous material closely encircling said core.

14. A covered rubber thread comprising a plu-' rality of parallel strands of rubber having flat longitudinal faces bearing against each other and bonded together to form astranded core, each of said faces being of greater width than the cross-sectional dimension of either strand at right angles to said respective faces, and a wrapping of fibrous material closely encircling said core.

15. A covered rubber thread comprising a rubber core having the cross-sectional form of a regular polygon but divided into a plurality of strands bonded together and each having substantially the same cross-sectional form, and a wrapping of fibrous material binding said strands together.

16. A covered rubber thread comprising a rubber core having the cross-sectional form of a regular polygon but divided into two strands similar in shape to each other and bonded together, and as wrapping of fibrous material tightly encircling said core.

17. A covered rubber thread comprising a rubber core having the cross-sectional form of a regular polygon but divided along a diagonal of said polygon into two strands of substantially equal section, said strands being bonded together, and a wrapping of fibrous material tightly encircling said core.

18'. A rubber thread comprising a plurality of parallel strands of rubber bonded directly together by a union which serves to hold them normally in a fixed longitudinal and lateral relationship to each other but does not integrally unite them, but which prevents the breaking of one strand from materially weakening another to which it is so bonded.

19. A rubber thread comprising a plurality of parallel strands of rubber bonded directlytogether, and a cover of fibrous yarn or thread wound tightly around said strands, the union between said strands serving to hold them normally in a fixed relationship to each other throughout the greater portions of their lengths notwithstanding the breakage of one strand but which prevents the breaking of one strand from materially weakening another to which it is so bonded.

GEORGE S. VAN VOORHIS. 

